This invention relates to an adjustment device and a lower limb prosthesis including such a device. The invention is of particular relevance to heel-height adjustment.
A known adjustable prosthetic joint for setting the angular position of a prosthetic foot with respect to a prosthetic shin component is disclosed in U.S. Pat. No. 5,957,981 (Gramnäs). This known joint comprises a pair of vane pistons located in fluid-containing chambers which are interconnected by a bypass valve allowing or preventing the passage of fluid between the chambers according to the setting of the valve. The assembly of the pistons, the chamber walls, and the rotary interconnection of the pistons and the chamber walls forms part of a prosthetic foot with a proximal clamp for receiving a shin tube. The valve is manually operable using a rotatable lever on the side of the assembly, allowing the prosthesis wearer to open the valve when angular adjustment is required.
A disadvantage of the known arrangement is that the assembly is bulky, particularly in the anterior-posterior direction. This and the incorporation of the assembly in the foot tends to restrict the choice of foot configuration available for the wearer.
A joint allowing dynamic hydraulic control of the angular position of a prosthetic foot with respect to a shin component is disclosed in Mauch Laboratories, Inc., Hydraulik Ankle Unit Manual, page 2, March 1998. This suffers from similar disadvantages.